Torsional energy absorber

ABSTRACT

A torsional energy absorber has inner and outer arm members connected by a pivot means. The pivot means has an outer tubular member fastened to the outer arm member, an inner member concentrically spaced apart from the outer member and fastened to the inner arm member, and an elastomeric member engagingly positioned between the inner and outer members, preferably under compression, to absorb energy on impact against the energy absorber by initially torqueing between the members and then slipping on the members. Preferably, the inner and outer members are cylindrical sleeves of like curvilinear cross-sections, and the elastomeric member is an annulus. In addition, it is preferred that a self-restoring means, such as a clutch assembly, be provided to restore the inner and outer members to original relative positions after impact.

111% Nemec States Patent [1 1 1 Mar. 5, 1974 [73] Assignee: The GeneralTire & Rubber Company, Akron, Ohio [22] Filed: June 23, 1972 [21] Appl.No.: 265,917

[52] US. Cl 267/140, 267/141, 267/153,

[58] Field of Search..... 267/571 R, 63 A, 140, 141, 267/153, 154;280/1045 A; 293/1, 84, 85,

[56] References Cited UNITED STATES PATENTS 1,565,882 12/1925 Adams293/86 1,633,901 6/1927 Ohlendorf 293/86 992,228 5/1911 McGregor 293/841,381,614 6/1921 Baumgartl 293/84 1,448,504 3/1923 Plante 293/841,619,087 3/1927 Pampinella 293/88 1,669,140 5/1928 Ohlendorp.... 293/841,704,995 3/1929 Williams 293/84 1,805,414 5/1931 Ohlendorp 293/84 Kolbe267/57.l R X 3,013,808 Willctts .l 280/1045 A Primary Examiner-Gerald M.Forlenza Assistant Examiner-Howard Beltran [57 ABSTRACT A torsionalenergy absorber has inner and outer arm members connected by a pivotmeans. The pivot means has an outer tubular member fastened to the outerarm member, an inner member concentrically spaced apart from the outermember and fastened to the inner arm member, and an elastomeric memberengagingly positioned between the inner and outer members, preferablyunder compression, to absorb energy on impact against the energyabsorber by initially torqueing between the members and then slipping onthe members. Preferably, the inner and outer members are cylindricalsleeves of like curvilinear crosssections, and the elastomeric member isan annulus. in addition, it is preferred that a self-restoring means,such as a clutch assembly, be provided to restore the inner and outermembers to original relative positions after impact.

4 Claims, 5 Drawing Figures IMPACT m-- PATENTED 51974 3.5.392

sum 1 OF 2 IMPA C T II-- ToRsioNAL ENERGY ABSORBER I FIELD OF THEINVENTION The present invention relates to an energy absorbing impactassembly and particularly a high energy absorbing bushing assemblyutilizing an elastomeric insert between a pair of rigid concentricsleeves.

BACKGROUND OF THE INVENTION Energy absorbers have been known and usedformany years. While many of these devices are utilized in a broad range ofapplication, they have not found practical utility in automobiles.Rec'ent attention has been focused upon protecting the automobile fromphysical damage which results from vehicular collision. Thus, it isproposed that automobiles be free from damage which might otherwiseoccur when a vehicle collides with an object at a predetermined speedand particularly at low speed, e.g. mph. Such devices require highenergy absorption without exceeding a maximum specified load, require aninexpensive and relatively small size package design, and involve anominal deflection on impact.

One apprach to the problem of achieving a high energy absorptiongenerally has been the use of a pair of members pivotally mountedbetween the impact member and the member to be protected. The pivotmeans of these devices includes such things as friction engaging plates,spring means, rubber members and the like to absorb the energy duringtherelative pivoting motion of the members. Illustrative of these devicesinclude US. Pat. Nos. 992,228, 1,381,614, 1,448,504, 1,619,087,1,669,140, 1,704,995 and 1,805,414. Such devices are particularlyadvantageous in their ability to withstand eccentric loading.

' Absorbers utilizing pivotal absorption means have been made to absorbimpact energy, but have not been found to have practical application inautomobiles. The amount of energy such devices can absorb whilerestricting package size is below that needed for automotiveapplications. Conversely, where such devices are large enough to meetthe energy absorption requirements, the device is not only too bulky andcumbersome, but requires loadings higher than can be practicallytolerated with automobiles and the like.

The present invention overcomes these difficulties and disadvantages andprovides an energy absorber utilizing elastomeric pivotal bushings whichabsorb large amounts of energy without exceeding a specified load ing.Further, the device can be adapted to return to its originalconfiguration without objectionable recoil and is an inexpensive deviceof small size.

SUMMARY OF THE' INVENTION An energy absorber of the present inventionhas inner and outer arm members connected by a pivot means. One of thearm assemblies is mounted, preferably pivotally, to a base such as anautomobile frame or the like. The other arm members are preferablypivotally secured to an impact member such as an automobile bumper.

The pivot means is comprised of an outer tubular member fastened to theouter arm members and an inner member fastened to the inner arm members.The inner member is concentrically spaced away from the outer member.Engagingly positioned between the outer and inner members is anelastomeric member which is adapted to absorb energy on impact againstthe absorber by initially torqueing between the members and thenslipping while under torsion on the members.

In the absorption of energy, the torsional stress-strain within theelastomeric member raises rapidly to a specific load value. Theelastomeric member then slips on the inner and/or outer membersabsorbing energy at an optimum, substantially constant rate as theimpact proceeds. In this way, large amounts of energy can be absorbedwithout exceeding a specified loading and with minimal deflection.

After impact, the energy absorber can be returned to its originalconfiguration by external means for reuse. Preferably however, aself-restoring means such as a clutch mechanism is provided as part ofthe energy absorber to return the inner and outer arm members to theirinitial relative positions. In this way, the energy absorber can providemulti-impact characteristics without the added time and expense ofreorienting the configuration of the absorber after each impact so thatit can be reused.

Preferably the inner and outer members are cylindrical sleeve membersfor convenience and expense of manufacture. In this connection, theinner and outer members have like curvilinear cross-sections selectedfrom the group consisting of circular and elliptic.

Other details, objects and advantages of the invention will becomeapparent as the following description of the present preferredembodiments and present preferred methods of practicing the sameproceeds.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, thepresent preferred embodiments of the invention and present preferredmethods of practicing the invention are illustrated in which:

FIG. 1 is a plan view of an energy absorber utilizing an elastomericbushing absorbing means;

FIG. 2 is an elevation view with portions broken away of the energyabsorber shown in FIG. 1;

FIG. 3 is a plan view of a self-restoring energy absorber utilizing anelastomeric bushing absorber means;

FIG. 4 is an elevation view with portions broken away of the energyabsorber shown in FIG. 3;

FIG. 5 is a graph showing the relationship of load to deflection of theenergy absorber shown in FIGS. 1 and 2 and of prior art devices.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2,energy absorber 10 has two inner arm members 11 and a clevis-shapedouter arm member 14 positioned relative to each other in an impact-freeconfiguration. Inner arm members 11 have end portions pivotally mountedin a pair relationship to an impact member 12, such as an automobilebumper, by a bolt assembly 13. Outer arm member 14 has an annularhousing 15 as the base of the clevis-shape. Outer arm member 14 has itsbifurcated end portions of the clevis-shape pivotally mounted to asupport member 16 such as an automobile frame by bolt assembly 17.

Inner arm and outer arm members 11 and 14 are connected by pivot means18. Pivot means 18 comprises an inner cylindrical sleeve member 19 andouter cylindrical sleeve member 22. Sleeve member 22 is concentricallyspaced away from and coaxially aligned with sleeve member 19. Engaginglypositioned between members 19 and 22 is annular elastomeric member 23.Elastomeric member 23 is radially compressed between inner and outermembers 19 and 22 by means well known in the art; see e.g. US. Pat. Nos.2,660,780, 2,684,524, 2,690,001, 2,872,727 and 2,877,543.

lnner and outer members 19 and 22 are fastened to inner arm members 11and outer arm member 14, respectively. lnner member 19 is fastened toarm members 11 by circular end plates 20 by welds, for example, at 21.End plates 20 are also fastened to inner arm members by any suitablemeans such as welding as shown. Outer member 22 is fastened to outermember l4 by concentrically engaging it within annular housing andfastening it to housing 15 by suitable means such as welding at 24 asshown. The particular manner by which arm members 11 and 14 are fastenedto inner and outer members 19 and 22 is a matter of choice and may bereversed. In other words, inner arm members 11 may be fastened to outermember 22 and outer arm member 14 may be fastened to inner member 19.

In operation, an impact imparted to impact member 12 causes inner armmembers 11 to deflect toward outer arm member 14. The relative movementof these members 11 and 14 are restrained by pivot means 18 whichabsorbs the energy of the impact in the following way:

lnner and outer sleeve members 19 and 22 are caused to rotate relativeto each other by reason of their rigid connections to inner and outerarm members ll and 14, respectively. The relative movement of members 19and 22 is permitted initially by torqueing of the elastomeric member 23until the impact loading reaches a preselected maximum value and then byslipping while member 23 is under torsion on members 19 and/or 22.

The angle at which the torqueing is discontinued and slippage iscommenced is called the slip angle. The slip angle is readily controlledby the hardness of the elastomeric member 23 and the extent of itscompression between inner and outer members 19 and 22. The hardness andcompression are in turn readily controlled by the composition oftheelastomeric material and the dimensions of the elastomeric memberrelative to members l9 and 22 before its insertion between members 19and 22. Typically the compositions of the elastomeric material is anyvulcanizable or curable rubber having a Shore A hardness below about 85and preferably above about 40. Typically the composition and compressionof the elastomeric member 23 is the same as that used inelastomeric-metal bushings for mounting internal combustion engines andthe like. The compression and hardness are preferably selected so thatthe slip angle is between about and 25.

After impact, the energy absorber 10 returns only part way to itsinitial configuration by reason of the torsional stresses within theelastomeric member 23. The energy absorbed by slippage is dissipated inthe form of heat and is not available to restore the absorber to itsoriginal, impact-free configuration. Additional forces must therefor beapplied to absorber 10 to return the arm members to their impact-freeconfiguration for reuse.

Referring to FIGS. 3 and 4, a self-restoring embodiment of the energyabsorber of the present invention is shown. The combination is the sameas that shown in FIGS. 1 and 2 except for the elimination of weldsbetween inner member l9' and end plates 20', the lengthening ofinnermember 19' as shown, and the additional elements hereinafter described.In this embodiment. circular end plates 20' are-free to rotate withinthe cylindrical inner sleeve member 19'.

Assembly 25 provides a means for restoring arm members 11 and 12 totheir relative, impact-free position after removal of the loading on theabsorber. Assembly or self-restoring means 25 includes a ratchet wheelhaving teeth 26 rigidly and concentrically mounted to one of endportions of inner sleeve 19 by key 27. Pawl 28 is pivotally mounted toinner arm member 11 by pivot assembly 29. During impact. pawl 28 engagesteeth 26 precluding rotation of inner sleeve 19 with respect to innerarm member 11'. Impact energy is thus absorbed by the relative rotationof inner sleeve 19' and outer sleeve 15' causing the elastomeric member23 to initially undergo torsion and then slippage (while under torsion)between the respective sleeves.

After removal of the impact forces, pawl 28 permits inner sleeve 19 tofreely rotate with respect to inner arm 11 to release the energy storedwithin elastomeric member 23'. By utilizing spring assembly 30comprising spring 31 compressively engaged between member 12' and 16 inseats 32 and 33, respectively, inner arm 11 and outer arm 14' can bereturned to their relative impact-free or unloaded position. Since innerarm 11' is free to rotate because of the relative position of pawl 28with respect to teeth 26, little spring energy is required. Preferably,the spring constant of spring 31 is low such that during impact littleenergy is absorbed thereby.

To illustrate the invention, energy absorbers similar to the one shownand described in connection with H68. 1 and 2 were tested statically,and dynamically with a pendulum weight. Three energy absorbers wereutilized, each capable of absorbing 15000 in-lbs. The inner diameter ofthe outer tubular members is 3 5/16 inches. The outer diameter of theinner tubular members is 2 inches. Axial lengths of the absorbers were 5inches, 3 inches and l A: inches respectively. Elastomeric members had aShore A durometer rating.

The results of the tests are set forth in Tables I and ll below.

TABLE I STATlC TESTS Axial Loading in Deflection Length of Absorberpounds where in inches in Inches slippage commenced at slippage 5 5200None 3 3 l I! 3 3200 L8 3 3350 L7 l /z I700 l.(?

The results show operability and repeatability with the slip load andslip angle repeating for the three test runs with the three inchabsorber.

Curve A of FIG. graphically represents the energy absorptioncharacteristics of absorbers of the present invention. The area underCurve A represents the total energy absorbed by the absorber. As shown,a maximum load of about 2400 pounds is achieved. Because of the featuresabove described, the load builds up rapidly to the maximum load and thenmakes a substantially smooth transition to a relatively constant load.This indicates the substantially constant force needed for slippage ofthe elastomeric member on the inner and/or outer sleeve members. Thus.energy is absorbed at a substantially constant rate during slippage.

Curves B and C of FIG. 5 are illustrative of the energy absorptioncharacteristics of comparable prior art absorbers. Curve B illustratesabsorption by a prior device of the same total energy as Curve A. 'Asshown, the prior device requires a peak load of about 2800 pounds toobtain the same energy absorption in the same deflection. In addition, alarger and heavier structure is required to withstand the higherloading. Conversely, as shown by Curve C, a comparable prior devicewhich does not exceed the predetermined load of about 2400 poundsabsorbs much less energy on impact for a given deflection.

While presently preferred embodiments have been shown and described withparticularity, it is distinctly understood that the invention may beotherwise variously performed within the scope of the following claims.

What is claimed is:

1. An energy absorber comprising:

A. outer arm members,

8. inner arm members,

C. a pivot means connecting said outer arm members to said inner armmembers, said pivot means having l. a tubular. rigid, outer sleevesecured to said outer arm members,

2. a tubular, rigid, inner sleeve disposed coaxially with and radiallyinwardly of said outer sleeve and secured to said inner arm members,

3. an elastomeric annulus radially compressed between said inner andouter sleeves and adapted upon impact to torque between said sleevesupon relative rotation between said sleeves about their axis up to apreselected angle and slip on said sleeves upon relative rotationbetween said sleeves about their axis of an angle in excess of saidpreselected angle.

2. An energy absorber as set forth in claim 1 comprising in addition:

d. self-restoring means for restoring the outer and inner arm members totheir original relative positions after impact.

3. An energy absorber as set forth in claim 2 wherein:

the self-restoring means is a clutch assembly. 4. An energy absorber asset forth in claim 1 wherein:

the inner and outer sleeves have like curvilinear cross-sectional shapesselected from the group con sisting of circular and elliptic.

1. An energy absorber comprising: A. outer arm members, B. inner armmembers, C. a pivot means connecting said outer arm members to saidinner arm members, said pivot means having
 1. a tubular, rigid, outersleeve secured to said outer arm members,
 2. a tubular, rigid, innersleeve disposed coaxially with and radially inwardly of said outersleeve and secured to said inner arm members,
 3. an elastomeric annulusradially compressed between said inner and outer sleeves and adaptedupon impact to torque between said sleeves upon relative rotationbetween said sleeves about their axis up to a preselected angle and slipon said sleeves upon relative rotation between said sleeves about theiraxis of an angle in excess of said preselected angle.
 2. a tubular,rigid, inner sleeve disposed coaxially with and radially inwardly ofsaid outer sleeve and secured to said inner arm members,
 2. An energyabsorber as set forth in claim 1 comprising in addition: d.self-restoring means for restoring the outer and inner arm members totheir original relative positions after impact.
 3. an elastomericannulus radially compressed between said inner and outer sleeves andadapted upon impact to torque between said sleeves upon relativerotation between said sleeves about their axis up to a preselected angleand slip on said sleeves upon relative rotation between said sleevesabout their axis of an angle in excess of said preselected angle.
 3. Anenergy absorber as set forth in claim 2 wherein: the self-restoringmeans is a clutch assembly.
 4. An energy absorber as set forth in claim1 wherein: the inner and outer sleeves have like curvilinearcross-sectional shapes selected from the group consisting of circularand elliptic.